1. Field of the Invention
The present invention relates to a system and method for automatically changing disposable nozzle tips used to dispense multiple component reactant mixtures.
2. Background Art
Multiple component reactant mixtures are used to form polymeric compositions. Examples of polymers formed by reactant mixtures include epoxies, polyurethanes and silicon compositions. For example, silicon seals may be formed by combining a two-part reactant mixture including a catalyst component and a base component that may be mixed and injected to form the silicone seal in situ in an assembly.
Reactant mixtures are normally mixed in a mixing chamber of a gun injector that dispenses the mixture through a nozzle. The speed of the chemical reaction may depend upon the type of composition and temperature of the reactant components. If the mixture is warmed or is not dispensed through the nozzle within the time allotted, the nozzle may become clogged. For example, the reactant mixture within the nozzle may react and cure inside the nozzle if the production line is slowed or stopped.
If the nozzle clogs, an operator is called upon to change the nozzle tip. The operator must remove the clogged nozzle tip, clean the injection gun mixing chamber, and replace the disposable nozzle tip. Manual nozzle changing operations are labor intensive and may require the operator to change the nozzle in close quarters. As with any manual service operation, the effectiveness and efficiency may vary from operator to operator.
Before Applicant""s invention, there was a need for a fully automated system and method of changing a disposable nozzle tip for a reactant mixture dispensing gun. Problems associated with the prior art as noted above and other problems are addressed by Applicant""s invention as summarized below.
According to the present invention a reactant material dispensing system is provided in which at least two components are combined in a dispenser having a disposable nozzle. The system includes a mixing head that receives two components under pressure from two separate sources. A mixture of the two components flows through a disposable nozzle that is received in a shroud that is detachably secured to a mixing head. A nozzle changing station is provided where the shroud and nozzle are removed as a unit from the mixing head. An ejector is provided for separating the nozzle from the shroud. A nozzle changer disposes of the clogged nozzle and replaces it with a new nozzle.
Other aspects of the invention as it relates to a reactant material dispensing system are that the two components may be a catalyst and a base that are used to form a seal, in situ, in an article manufacture. The nozzle may be an elongated plastic nozzle having a static mixing element disposed inside the nozzle. The shroud may be a rigid elongated member having an elongated cavity in which the nozzle is received. The shroud may be connected by a threaded collar to a complimentary threaded portion of the mixing head.
According to other aspects of the invention, the mixing head may be connected to a robot arm that moves the mixing head between a production station and the nozzle changing station periodically to permit changing of the nozzle. The nozzle changing station may include an ejector pin that is inserted into the shroud and contacts the nozzle to eject the nozzle from the shroud. The nozzle changing station also may include a gripper that engages a used nozzle to remove the nozzle to a disposal station. The nozzle changer may also include a second gripper that selects a new nozzle from a magazine and moves it to the shroud.
According to another aspect of the invention, a method of changing a nozzle for a reactant material dispensing machine is provided. The reactant material dispensing machine is used to dispense at least two component materials that are combined and then dispensed by a mixing head. The dispensing machine includes a nozzle that is detachably retained on the mixing head by a shroud that is selectively removable from the mixing head. The method comprises moving the mixing head to a nozzle changing station, disconnecting the shroud and nozzle from the mixing head, and ejecting the nozzle from the shroud. The used nozzle is gripped and removed from the shroud. A new nozzle is then placed in the shroud and the shroud and new nozzle are reassembled to the mixing head.
According to other aspects of the method of the present invention, the step of disconnecting the shroud and nozzle from the mixing head may include engaging the shroud with an automatic wrench such as a nut runner that disconnects a threaded collar used to secure the shroud to the mixing head. The step of ejecting the nozzle from the shroud may be performed by inserting a pin through the shroud that engages the tip of the nozzle to separate it from the shroud. The step of gripping the new nozzle may further include selecting a new nozzle from a magazine. The step of reassembling the shroud and new nozzle to the mixing head may include placing a new nozzle within the shroud and automatically turning a threaded collar that secures the shroud to the mixing head.